Do not access ISA timer if BIOS reports that there is no legacy devices present.

[kib]

Summary

I did not committed this because on the computer where ISA timer is gated, bios really reports that ISA devices are present.
But I think now that acpi_get_fadt_bootflags() is useful on its own.

[royger]

I would like to use acpi_get_fadt_bootflags for vt also, but then it needs to live in some generic ACPI file, or else I would have to provide dummy implementations for !x86 arches.

[kib]

In D16004#338788, @royger wrote:

I would like to use acpi_get_fadt_bootflags for vt also, but then it needs to live in some generic ACPI file, or else I would have to provide dummy implementations for !x86 arches.

I do not see why, the code is already protected by x86 checks.

[kib]

Convert vt_vga.c to use acpi_get_fadt_bootflags().

Also initialize ignore before TUNABLE_INT_FETCH(). Otherwise, if there is no kenv var, the local is uninitialized.

[royger]

LGTM thanks.

sys/dev/vt/hw/vga/vt_vga.c

51 ↗

(On Diff #44413)

Not sure if it's a phab issue, but I think the last defined is missing the closing ')'. ie: defined(__i386__)

[kib]

The rest of the patch.